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Thread: Rough idle after warm up. Hrmm...

  1. #1
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    Rough idle after warm up. Hrmm...

    So I've been having a rough idle ever since doing my vanos job. I've been lazy about it because it hasn't really been all that noticeable. Recently, it has gotten worse.

    The curious part is it idles fine on a cold start, but starts to get rough once it warms up. The tach says the idle is stable, but when I put the car into reverse to back out of the garage, I notice a significant rpm loss and then a sudden surge back up to normal.

    The only info I could dig up was relating to rough idle on a cold start.

    The lower the RPM, the worse it is.
    Idle is smooth on a cold start. Starts to get rough as soon as I hear a sort of suction sound like a valve closing. Usually about 1-2 minutes after a cold start. Idle is less rough with the AC on.

    The car always stays running though. It's never stalled on me. No SES light or codes either.

    I ran a diagnostic in DIS a few months ago, but I was mostly concerned with a timing issue and the thread sort of fizzled out into a discussion on smoke machines. Here's the info I obtained relating to the rough idle.





    DIS suggested the tank venting valve. I'm thinking CCV, but each part is like $80 and I don't want to blindly throw money at the issue.

    I can't seem to get the software working again, so I can't do another diagnostic. In the meantime, does anyone have any experience with an issue similar to mine?
    2003 540i/6

  2. #2
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    unplug the vent valve to intake horn hose and see if it gets worse (as far as discarding/confirming the vent valve)
    Also, have you checked your idle valve? Holds vacuum like it should? It's properly plugged in? Electrical and vacuum wise, I mean.
    Have you ever replaced/checked/upgraded something in the headers? (pre cats wise)
    Fuel filter and pump are checked? Rail pressure?
    Diehard E39 driver.
    I'd rather die or take a walk before driving an E60 or any BMW made after Y2K.
    ​"Your momma's so ugly she makes Bangle cars look nice"

  3. #3
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    Quote Originally Posted by jicaino View Post
    unplug the vent valve to intake horn hose and see if it gets worse (as far as discarding/confirming the vent valve)
    I just checked. No noticeable difference. I hooked it back up and then unplugged the wire from it. Still no difference.


    Quote Originally Posted by jicaino View Post
    Also, have you checked your idle valve? Holds vacuum like it should? It's properly plugged in? Electrical and vacuum wise, I mean.
    I have a vanos engine, isn't ICV only on the non vanos engines?


    Quote Originally Posted by jicaino View Post
    Have you ever replaced/checked/upgraded something in the headers? (pre cats wise)
    Nada.


    Quote Originally Posted by jicaino View Post
    Fuel filter and pump are checked? Rail pressure?
    No, no, and no.


    Also, there's a slight hissing noise coming from the CCV area. Not sure if that's supposed to be quiet back there or if a slight hissing is okay.
    Last edited by waters17; 09-12-2016 at 09:17 PM.
    2003 540i/6

  4. #4
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    The idle valve, what a brainfart. The vacuum check valve, solenoid and control valve, and all hoses involved here: (sorry the only picture I liked was of a B46 engine which has an additional vacuum control solenoid)


    If something is wrong there, you could have an artificial exhaust leak caused by the SAP circuit. It will idle like shaky and hunting. Another possible culprits are the booster check valve and hose, which has a very kinked bend and it when it cooks dry and brittle sometimes cracks creating a nasty leak that bothers mostly at idle, and the CCV itself. Pull out the dipstick while idling, if it speeds up your CCV is gone. Also feeling for vacuum out of the dipstick tube. It should have an ever so slight pull, not suck like... Well, out of metaphoric finesse. It shouldn't suck like "what do you want for your birthday" but more like a lost bet (barely and relentlessly)
    Diehard E39 driver.
    I'd rather die or take a walk before driving an E60 or any BMW made after Y2K.
    ​"Your momma's so ugly she makes Bangle cars look nice"

  5. #5
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    I'll check the hose routing when I get home tonight. I did replace the yellow/blue striped hoses with some off the shelf vacuum hose from the auto parts store, but nothing else was changed. I'm confident they're hooked up correctly, but It's a good idea to double check.

    The slight hissing noise I hear seems to be coming from the booster check valve or CCV. It's tough to tell with all the extra motor noise.

    The dip stick tube does have some suction, but I'm not sure how to gauge it. (other than your provocative description) When I remove the oil filler cap, I can hear a slight vacuum sound once I start loosening the cap.

    ------------begin edit---
    I checked the idle rpm with the Torque app at lunch. Normal idle is between 560-600rpm. I pull the dipstick out and the idle says pretty much the same.
    Last edited by waters17; 09-13-2016 at 12:22 PM.
    2003 540i/6

  6. #6
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    I connected the car do DIS, Rheingold, and INPA last night and I got like 27 errors/warnings, but no codes. Most of the warnings were related to electrical issues with things like the seat warmer, DSC, steering angle, secondary water pump, etc.. I was also having issues with DIS not autodetecting the car. A few months ago, it was working perfectly.

    DIS gave me a warning suggesting that the engine wasn't able to start, but it was running when I did the scan. Not sure where to go from there.

    My research suggests a bad battery, but would that contribute to my rough idle?

    Then things got exciting!
    I was running another simple test scan in DIS and the laptop battery died mid-test. I turned the car off, then back on. Suddenly, it's showing me Engine Failsafe Program, and the idle keeps jumping back and forth from 500rpm to ~1500rpm.

    While panicking, I hooked it back up to INPA and cleared the codes/warnings, and reset all the adaptations. The car started up fine after that. I went to bed.

    This morning I started the car and it went back into the failsafe program. Again, I reset everything with INPA and it started fine. I drove about 45miles to work with no issues. I didn't try to start the car again once I got to work, but I'll try again at lunch, and I bought the laptop just in case.

    I sure hope I didn't do any damage with the laptop dying mid-test. Anybody know what's going on with this thing?
    2003 540i/6

  7. #7
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    Doubt the laptop going dead would have caused any issues.
    I use to get the same failsafe with the idle surging up to 1500, shut it off and restart and it would be fine for many months. It hasn't done it in ~2+ years, never found out what or why.
    Check the car battery voltage before you start the car at lunch and then again just after you start it, not running it should be 12.5 v or above. Running should be above 13 v just after you start it. Could be as high as 14 v, just depends on the RPM, the condition of the battery, etc.

  8. #8
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    Thanks.

    I checked with the OBC.
    12.1V - Before starting the car
    13.2V - Running

    Is that close enough to normal, or is the battery on its way out?
    2003 540i/6

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    Bad battery...


    '00 540iA Sport w/235k+ Original TCG's, Vanos and transmission.​*Trans failure at 244k+...FS Now

  10. #10
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    Close enough. Thanks!

    I'll pick one up tonight.

    Now back to my rough idle issue...
    2003 540i/6

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    Could be due to the low batt...wait until you replace and go from there.

    '00 540iA Sport w/235k+ Original TCG's, Vanos and transmission.​*Trans failure at 244k+...FS Now

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    13.2 running will cause all sorts of whacky codes. Listen to the violinist.

    BTW I just gave money to my niece to buy a violin as she wanted to start learning (plays flute and piano as well) and my sister is a pianist (also played cello, clarinet and violin as a child but piano was her career calling) so it makes sense....but damn they are expensive. IDK why people have kids....on purpose.

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    Quote Originally Posted by Flounderasu View Post
    13.2 running will cause all sorts of whacky codes. Listen to the violinist.

    BTW I just gave money to my niece to buy a violin as she wanted to start learning (plays flute and piano as well) and my sister is a pianist (also played cello, clarinet and violin as a child but piano was her career calling) so it makes sense....but damn they are expensive. IDK why people have kids....on purpose.
    Trying to save the OP a few dollars...

    Regarding your other statement. I'll bet what you think is expensive...isn't!

    A colleague just bought a violin in France (cheaper over there) and dropped $35k (no case, no bow and that's "cheap"). Another has a violin worth over $150k and it just keeps going UP... At AUCTION, violins can go for over $8 MILLION...yes, you read that correctly! It makes having a great instrument (for a professional), almost impossible...

    After knowing that, is my first statement correct?

    '00 540iA Sport w/235k+ Original TCG's, Vanos and transmission.​*Trans failure at 244k+...FS Now

  14. #14
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    Heyyy now... Don't be jackin' my thread.
    2003 540i/6

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    Quote Originally Posted by waters17 View Post
    Heyyy now... Don't be jackin' my thread.
    Nothing worse than being jacked by another man!!

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    Quote Originally Posted by Mannyf540 View Post
    Nothing worse than being jacked by another man!!
    Well yes there's worse. You could be jacking another man.
    Diehard E39 driver.
    I'd rather die or take a walk before driving an E60 or any BMW made after Y2K.
    ​"Your momma's so ugly she makes Bangle cars look nice"

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    Apologies Waters! I certainly don't want to be "jackin" ANY man...EVER!

    '00 540iA Sport w/235k+ Original TCG's, Vanos and transmission.​*Trans failure at 244k+...FS Now

  18. #18
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    Fix battery first. Vent valve as long as it opens and closes won't cause the issue. I have a spare one that was intermittent so I swapped it out if you want me to send it to you.

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    Word play is fun. No worries, V, I'm just messing around.

    Whelp, I installed a new battery. I trusted the OBC, so I didn't bother to get the old one checked first. Installed the new battery, attempted to start it, got the engine failsafe idle thing again. Was in the parts store parking lot, so I panicked a little bit.
    I cleared the codes, and got the failsafe AGAIN! It then occurred to me that the car ran better with the AC on, so I turned the AC on, and the car started right up. I checked the voltage on the new battery, and it was reading 11.xx. I drove home. I read somewhere that it's a good idea to charge a new battery before using it, so I took the new battery to the parts store to get it checked, and it's 100%.

    The car still functions, so I'm not super upset, but man, this is really eating at me. Did I just blow a bunch of money on a battery for nothing?! Lookin' at you, V...

    Diagnostics software isn't much help since it's only giving me a ton of unrelated and possibly false errors. Bad wiring maybe?
    2003 540i/6

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    Quote Originally Posted by waters17 View Post
    Word play is fun. No worries, V, I'm just messing around.

    Whelp, I installed a new battery. I trusted the OBC, so I didn't bother to get the old one checked first. Installed the new battery, attempted to start it, got the engine failsafe idle thing again. Was in the parts store parking lot, so I panicked a little bit.
    I cleared the codes, and got the failsafe AGAIN! It then occurred to me that the car ran better with the AC on, so I turned the AC on, and the car started right up. I checked the voltage on the new battery, and it was reading 11.xx. I drove home. I read somewhere that it's a good idea to charge a new battery before using it, so I took the new battery to the parts store to get it checked, and it's 100%.

    The car still functions, so I'm not super upset, but man, this is really eating at me. Did I just blow a bunch of money on a battery for nothing?! Lookin' at you, V...

    Diagnostics software isn't much help since it's only giving me a ton of unrelated and possibly false errors. Bad wiring maybe?
    Check your throttle body gasket. You may have an intake leak somewhere along the the intake or throttle body.

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    I didn't see failsafe mentioned before. Anyhow - check the V underhood - could be alternator. SB above 13.8.

    13.2 while running could be alt or battery - mine was battery that was causing excessive load on alternator causing falisafe and codes - but since you got a new battery and you said it's fully charged then it shouldn't be straining your alt unless it's goin bad or your terminals are loose/corroded

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    Doesn't sounds like a real problem, sounds more like a bunch of gremlins set loose by low voltage. Did you register your new battery? It might seem a stupid consideration but what it does is regulates the charge cycling so your new battery lasts longer. IME an unregistered battery lasts for about 2 years and then's toast. A registered battery, I've heard of OEM lasting for over 8 years. The last one I replaced had 6 years under its belt. I didn't bother registering it and the next one lasted way less than 2 years.

    Hard reset it and if you have one, put a slow charger/conditioner to be sure your battery is 100%. Leave the neg out and don't do that "touching (+) and (-) cables together" thing. Just disconnect your (-) and step on the brakes for 15 seconds.

    It wouldn't hurt checking all your wiring (engine compartment, DME and EGS box, various ground straps, fuses, etc)
    Diehard E39 driver.
    I'd rather die or take a walk before driving an E60 or any BMW made after Y2K.
    ​"Your momma's so ugly she makes Bangle cars look nice"

  23. #23
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    The OBC is still giving me low readings for voltage (12.1V) with the car off, but INPA is telling me 12.45V. Why the difference?

    I should have noted earlier that the 11.xx reading was also with the car off. The drive home held pretty steady at 13.8V with the AC on. AC off, it fluctuated between 13.2 to 13.6

    I scanned again in DIS this evening, and I was getting all those gremlin faults again. As a temporary bandaid, I adjusted the idle rpm to ~660. I scanned again, and the DME was the only thing that was showing faults. Those faults are circling me back to a post I had a few months ago after I did the vanos job.

    I ran the smooth test & actual/nominal test, and it looks like I might still have a timing issue. No SES light, but the diagnosis suggests otherwise.





    DIS suggests running a "Mixture Preparation" test, and I wanted to do it tonight, but I'll have to leave the engine running for 30 seconds at 3500rpm.. The muffler delete makes that somewhat difficult to do at night with out upsetting the neighbors.

    In my previous post GearGrinder had also suggested the throttlebody. I completely forgot about that. The thread eventually trailed off into comparing rough idle numbers and then to smoke machines.. I must have gotten burned out or distracted by something else. -Oh god.. Am I one of those ******* guys that asks for advice on the forum and then doesn't listen?!

    Also, I could not find a place to register the battery. I searched google and came across a post that said the e39 doesn't have that function.
    http://www.bimmerforums.com/forum/sh...y-registration


    I have to drive to Illinois this weekend for a stupid wedding for people I don't even know, and visit with family. I'll be bored out of my mind, so I'll have plenty of opportunity to run some tests and check some things.

    Course of action:
    Run the noisy mixture prep test.
    Run TESTO while spraying the motor with combustible chemicals and monitor results. (hopefully something will show up in an easy to access location, such as the suggested throttle body)
    Verify vacuum hose routing is correct.
    Check actual battery voltage directly from the battery and then from under the hood.
    Check for bad wiring connections.

    Also, I don't have a battery charger. My sister's boyfriend might though.
    2003 540i/6

  24. #24
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    Have you verified oil level? Are you near a due oil service? I'm asking because I had a bunch of issues with compatible symptoms and my vanos actual/nominal comparison looked pretty much the same as yours. Is your exhaust smelling particularly funky?
    Also if you don't mind, do you remember the idle speed adjust menu? (How to get there?) I adjusted it the other day and today while trying to access it again to doctor up some values I wasn't satisfied with it says "no such measures for ME 7.2"... I'm like Wtf?? I know I adjusted it before. Maybe I'm having a bad day.
    I couldn't find the battery registration thing in DIS when I looked into it. Have you tried INPA?
    Diehard E39 driver.
    I'd rather die or take a walk before driving an E60 or any BMW made after Y2K.
    ​"Your momma's so ugly she makes Bangle cars look nice"

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    Quote Originally Posted by jicaino View Post
    I couldn't find the battery registration thing in DIS when I looked into it. Have you tried INPA?
    No battery registration for E39's.

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